What Caused The Younger Dryas Cooling, Megafauna Extinctions, & Clovis Disappearance? GEO GIRL

If a mass extinction-causing asteroid or comet impact happened in the last 15,000 years, we would know about it, right? Not quite... There is still major controversy about an impact that may or may not have occurred around 12,900 years ago. In this video, we discuss the hypothesis that an impact caused major climate change and extinctions around 12,000 years ago, which is called the Younger Dryas Impact Hypothesis (YDIH).

0:00 What was the Younger Dryas?
1:11 When was the Younger Dryas?
2:55 Unknown cause of Younger Dryas?
3:58 YD Impact Hypothesis
4:55 Impact evidence
7:20 Missing evidence
10:21 Extinction of Clovis people?
11:31Extinction of megafauna?
13:02 Is there a crater?
14:21 Other causes of the YD cooling
15:04 Ocean circulation cause
18:43 Similar ocean circulation changes today
21:03 Summary of YD Impact Hypothesis

References:
YDIH specific refs:

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[johnholly]

I watch a lot of geology, anthropology, archeaology, history, and science channels on YouTube. I enjoy your channel, it’s one of my favorites. Thank you.

[damienbosse]

Thanks for your videos! I was able to get my professional geology license in no small part to watching all your videos on repeat. Such good content and your presentation is great!

[stuartvyse]

Super nice summary of the YD cooling event. One puzzling thing about the YD, that has been the focus of my research and others who work in Chukotka, NE Siberia and parts of Alaska, is the apparent absence of a YD cooling in quite a few lacustrine and terrestrial depositional records.

[TateFM]

Your presentation only seems to get better with each video. Love your content and I learn so much with each video. It's so easily digestible as a layman.

Also great bedtime/sleep video as well. Looking forward to the next one!

[a.randomjack]

I really appreciate all those clarifications. Excellent research .You rock Dr. 👍

[parksto]

The cat: "Dont Youtube. PET ME NEOW" 😸

[vindemiator]

Younger Dryas sounds like it could be a Jethro Tull song title.

[paintbrush]

Yes! One of my favorite topics!!! Thank you for another great video!

[moemuggy]

As an avid Native American projectile point collector, I can assure you the Clovis never went anywhere. We can see a direct progression in lithic types spanning thousands of years without interruption.
First Clovis, then Redstone, Folsom, Cumberland, Beaver lake, Dalton, etc, etc.. All very closely related.
In fact, they're still here.

[barbaradurfee]

You continue to amaze me given your busy busy life. I loved this video & I also loved your strategic call today, the reaction here was actually acceptance 😊😉 and acknowledgement of your good judgement. ❤️

[posticusmaximus]

You're the 4th or 5th YT paleontology channel (Eons, Raptorchatter, North02, et al) I've seen having to debunk the YDIH; and have done the best job explaining it. The visuals help a lot!

[andybreckenridge]

A few corrections/comments:
1) you showed reconstructed temps is Greenland to explain the Younger Dryas (YD) - those are not global temps. Temperatures did not decrease in the southern hemisphere during the YD. Note that sea levels rose during the YD, so the ice sheets continued to melt during the YD. Global temperatures warm during at least the later half of the YD.
2) Because the YD is ~1300 years long, I have not seen any claims of a meteor/comet-induced (or volcanic) global winter connected to YD cooling. Impact or volcanic cooling would be very short-lived (less than a decade). The YDIH papers generally avoid explaining how an impact caused the YD, and instead focus on evidence of an impact around the YD.
3) There's no question that the Atlantic Meridional Overturning Circulation disruption is associated with the YD, and would cause cooling in the north hemisphere (esp. Greenland and Europe) and warming in Antarctica. The YDIH needs the impact to affect the AMOC to be relevant to YD cooling.
4) The ice sheets were shrinking long before the Bolling-Allerod (B/A) - global sea level rise is a good proxy for meltwater production, and sea level starting rising around 20, 000 years ago (the B/A starts around 15, 000 years ago).
5) its the shift in meltwater drainage in North America that would affect the AMOC. As the Laurentide Ice Sheet shrinks to within the Arctic drainage basin, a major component of meltwater would be routed away from the Gulf of Mexico into the Arctic and/or St. Lawrence (Atlantic) watersheds. This would happen at the end of every glacial cycle.

[caspasesumo]

Thanks - very cool and objective coverage of the YD. I read somewhere that the YD also caused arid conditions in the fertile crescent that led to, or at least coincided with, the origin of agriculture.

[neleig]

Thanks for speaking theoretically and indicating more study and data is needed. It’s so refreshing. Belief in Science has been damaged over the years by claims that theories are facts.

[danwylie-sears]

It occurs to me that a spike in iridium concentration in a rock layer doesn't necessarily have to mean a single large impact. It could still be from a sudden influx of iridium, but that iridium might have arrived in multiple objects. We have the various meteor showers (leonids, perseids, etc.) from objects that left a lot of material in an orbit that intersects ours. Given iridium's status as a siderophile, I expect it to be much more abundant in metallic objects derived from the cores of differentiated protoplanets, than in the kind of outer-solar-system objects that cause meteor showers. But if a high-eccentricity object such as a comet collided with a low-eccentricity one that could be metallic, a large amount of iridium could be left to arrive as meteor showers, with centuries' worth arriving over a few decades. Or a comet could just be so large that its meteor shower leaves enough material to produce a measurable iridium spike.

Alternatively, it might be possible, given a sufficiently stable location, get a small local iridium spike by having deposition from terrestrial sources cease for decades while meteor dust continues to arrive at the usual rate. I imagine a snow field that accumulates year after year on flat land, getting almost thick enough to flow as a glacier but not quite, in an area with lower than average influx of terrestrial dust. Outflow of melt water could concentrate the meteor-enriched dust from the snow field in a few locations at the edge.

[ronaldbucchino]

Thank you, Doc, -- another fascinating presentation -- my side focus in grad school was the old KT impact -- and all the subsequent impact events -- I look forward to all your ideas.

[terenzo]

Your cat is always welcome to make an appearance.

[ArnoSchlick]

Very good Video, I do like the scientific style. My summary: At least the "Meow-Fauna" is still quite alive, as we can see. 😅

[tuffymartinez]

Thank You Dr. Rachael. Wow second episode in just a few hours. That means when I focus on "Geo Girl" my thinking cap is on my peanut brain and I am trying to absorb as much as possible, whew..TM

[mikeclarke]

The latest YDIH I heard is that it was probably Percids meteor shower, with a chain of small impacts across northern american ice shield. This resulted in local shock diamonds and iridium deposits, but the combined effect added up to global cooling, maybe included another big impulse of fresh water leading to ocean circulation shutting down. "shrugs"